1. Field of the Invention
This invention relates generally to warning systems and, more specifically, to a Low Pressure Warning System that provides extremely efficient, long-term performance.
2. Description of Related Art
Vehicle low-tire-pressure warning devices and systems have been available for many years. In general, these systems provide an alert to the operator of a vehicle in the event that the pneumatic pressure in one or more of the vehicle's tires has dropped below a pre-determined safe level. These systems and devices are particularly appropriate in multi-axled vehicles, such as commercial 18-wheeled vehicles, because they typically are impacted severely in the event of a flat tire. Since these vehicles are not typically equipped to change their own tires, they must call for outside assistance and then wait for the repairs to take place; this process is typically very time-consuming (and consequently expensive). If there were a warning device that would alert the driver of a low tire pressure condition before the tire beat itself to death on the rim, the driver might have the opportunity to make a controlled stop at a gas station or the like, where the repairs could be effected more quickly. This would also prevent damage to the tires that are adjacent to the defective tire.
A significant problem with any prior tire pressure alarm system is that of longevity. If the monitor is small enough to be placed internal to the tire, it must have its own electrical power supply. Most prior systems impose a constant current draw on this local power supply (or battery) while simply monitoring the normal pressure conditions within the tire. Consequently, the battery is in use at all times, and its life is unacceptably short. What is needed is a tire pressure monitoring and alarm system that is able to monitor the tire's pressure without imposing any current draw on the local power supply in so doing.
Examples of prior, unsuccessful, tire pressure monitoring and warning systems are Williams, U.S. Pat. No. 5,109,213, Nowicki, et al, U.S. Pat. No. 5,285,189 and Mendez, et al, U.S. Pat. No. 5,463,374.
Williams discloses a complicated, expensive systems that will be difficult to maintain over the working life of a vehicle. Specifically, the Williams device uses battery power while tire pressure is in its normal operating range. This means that the battery on each wheel would require replacement several times during the ten-year shelf life of the battery. Furthermore, the device is installed on the fill stem for pressurizing the tire, and as such, is exposed to the environmental elements, not to mention theft. Still further, the Williams device is rather large, and as such will make balancing the wheel difficult once it is installed. Also, since the Williams device installs on the stem, it is subject to gas leaks, which will itself cause the tire to go flat|
The Nowicki device seeks to reduce power draw on the local power supply by incorporating a centrifugal switch that disables the system (and power draw) when the wheel is not rotating at a rate indicating that the vehicle is in service. The drawback of this method is that most commercial vehicles spend a great deal of time in service, driving around. During these times, the Nowicki device will be energized and will draw power from the battery, even when the tire is at a safe pressure.
The Mendez, while combining several other alarm features beyond tire pressure warning, also fails to disclose or imply a device that functions to solve the longevity problem. Although the Mendez device does use a low battery current, this draw, like Nowicki and Williams is present even when the tire is at its normal operating pressure. Furthermore, the Mendez system is not a practical solution for most vehicles, since it is actually part of the original equipment of the vehicle; it is not feasible to install the Mendez system into a wide range of vehicles already on the road.
The device and system of the present invention, as detailed herein, solves all of these problems while further providing other advantages over any other relevant system elsewhere disclosed or implied.